In a gas chromatograph, a carrier gas is introduced into a column from a sample introduction part together with a sample, and each sample component is separated in a process that the carrier gas passes in the column. Each sample component separated in the column is detected by a detector connected to the column. The connection of the column to a sample introduction part or a detector can be performed via a column-attaching device.
The column-attaching device is provided with, for example, a ferrule, a ferrule receiving part, and a ferrule pressing part. The ferrule is attached to the column by being swaged in a state in which the column is inserted. And, by fixing the ferrule attached to the column by sandwiching between the ferrule receiving part and the ferrule pressing part, the column can be attached to the column-attaching device (see, for example, the following Patent Document 1).
In a conventional column-attaching device as exemplified by Patent Document 1, a ferrule pressing part is screwed in the ferrule receiving part to be attached thereto. Concretely, screw threads are formed on the inner peripheral surface of the cylindrical ferrule receiving part, and screw grooves are formed on the exterior peripheral surface of the tip end part of the ferrule pressing part to be screwed in the ferrule receiving part.
As for ferrules, ferrules different in shape are used depending on the outer diameter of a column to be inserted into a ferrule. Therefore, depending on the shape of ferrule to be used, the screwing amount of a ferrule pressing part to the ferrule receiving part changes. For this reason, on the inner peripheral surface of the ferrule receiving part, screw threads are formed in a relatively wide range, and by screwing the ferrule pressing part to an appropriate position depending on the shape of the ferrule, it is possible to press the ferrule toward the ferrule receiving part with a sufficient pressing force for securing a sealing performance.